'A -20 



VEliTEBKATE ANIMALS. 



one of the muscles of the abih^meu. There are no external ears. 

 Tlie mammary glands have no niiijiles, but open either on a flat sui'- 

 face {Oniithorhi/achus), or into a small " mammary punch " (^cAi'fZma). 

 It has recently been shown by Mr Caldwell that the Munotremes are 

 not viviparous, a.s all other Mammals are, but that tliey resemble 

 the Reptiles and Birds in being oviparous. The Duck-mule lays two 

 eggs— about three-quarters of an inch in length— which it deposits 

 in the burrow in which it lives ; and the Echidna lays one such egg, 

 whicli it is stated to place in the small pouch of skin siuTounding the 

 openings of the mammary glanils. Recent observations also show 

 that the Monotremes further resemble the Reptiles in the fact that 



Fig. 221'..— A, Skull of Eriihhui Inislrix. B, Siile view of tlie skull of Ornilliorliynchiti 

 2«7,',/Wr.;-,<s, ;iih1 (J, ]n\\t'f jaw nf tliu Siimc, \ ic\vc<l tVolii .'ilinVL', sliuwilig tlie boiliy 

 ilfUtal l.hitfs (/,/). 



the temperature of tlie body is much below that of the remaining 

 types (jf the Mamiuals. 



Of the two living genera uf Munutreuies, the Duck-nu>le {Oniitkn- 

 rlii/iirliiix) is found cxcbisively in Au.stralia inh.-ibiting streams and 

 ]iunds, ill the banks uf wliicli it cnu.structs burrows furty or fifty feet 

 in length. The body is bke th.il uf a small Utter, covered with a 

 short bruwii fur, anil having a binad llatteneil tail i'fig. 2271. The 

 j.aws h.ave nu teetli, but cany hurny |il,-ites, which <itlici;ite as teeth 

 (Hg. i-lC}, B ;ind ('). The margins of the j.-iw are nlsu sheathed in 

 liorii, foiiiiing .-I, kind uf tintteiied beak, very like that of a Duck 

 nig. -I-ll '. Mriicr the n.anie uf " I )nik-liilled Animal" sometimes 

 given tu tlic ()riiilli(irli;jiiclui.s. The feet are webbed, and the males 



